The invention relates to a method for the ozonolysis of unsaturated fatty acids and derivatives thereof, and to a method for removing reactive oxygen species from a reaction mixture comprising ozonolysis products of an unsaturated fatty acid or of a derivative thereof.
Ozonolysis is a method established in synthetic organic chemistry for cleaving a C═C double bond of an unsaturated hydrocarbon to form two carbonyl compounds. The latter may in particular be carboxylic acid, aldehydes and alcohols. In mechanistic terms, ozonolysis involves a [3+2]-cycloaddition of the ozone onto the double bond, which gives a primary ozonide, an unstable intermediate, which decomposes to give an aldehyde and a carbonyl oxide. The latter can either polymerize and/or dimerize to give a 1,2,4,5-tetraoxolane or, in a further cycloaddition, form a secondary ozonide. The secondary ozonide can then be worked-up oxidatively to give a carboxylic acid or reductively to give an aldehyde. The aldehyde can be reduced further as far as the alcohol (Vollhardt/Scholer, 1995).
A disadvantage of the method is that from the carbonyl oxide is formed not only the secondary ozonide, which can be worked-up to give the desired products, but also a number of by-products, including the tetraoxolane dimer, an adduct, referred to as hydroperoxide, of ozonide and water and also hydrogen peroxide produced therefrom. Moreover, the formation and accumulation of secondary ozonide is unacceptable with regard to the safety of the reaction implementation since compounds of this type are known to be explosive.
The formation of the other by-products lowers the yield of the reaction, especially since the hydrogen peroxide produced is also able to oxidize products of subsequent steps and, in so doing, to form additional by-products. Undesired carbonyl compounds that are formed can lead to the formation of numerous undesired condensation products.